Group by

[email protected] (Philip Thompson) Wed, 9 Dec 2009 09:52:31 -0600

Newsgroups	php.db
Message-ID	<[email protected]>

Hi.

In a mysql query, it is recommended that "GROUP BY" fields be indexed? Using EXPLAIN on one of my queries, I noticed no change between having indexed by GROUP BY field and not indexing it. Any thoughts would be appreciated.

In this example, should `history_field` be indexed...?

SELECT MAX(`timestamp`) AS `max_ts` 
FROM `history` 
WHERE `req_id` = 17 AND `history_record_id` = 35
GROUP BY `history_field`

Thanks,
~Philip